This invention relates to an AC disconnect switch, and more specifically relates to an AC disconnect switch having an enclosure with an internal terminal block assembly that is easily accessible for installation of wiring, that is adaptable to installation in inaccessible locations, and that has an improved locking mechanism.
AC disconnect switches are well-known in the art and are often used for connecting AC current to and disconnecting AC current from air-conditioner compressors. Such AC disconnect switches operate between on and off conditions by inserting a pullout handle assembly into and removing the pullout handle assembly from a stationary terminal block assembly mounted within the enclosure of the AC disconnect switch. The pullout handle assembly has conductive blades which engage stationary stabs within the terminal block assembly to thereby complete an electric circuit. Such AC disconnect switches may or may not incorporate fuses within the pullout handle assembly.
Although AC disconnect switches come in a variety of mechanical designs, a typical design is shown in Miller et al. U.S. Pat. No. Re. 34,113. The disclosed AC disconnect switch includes an enclosure comprising a rectangular shaped case with a hinged cover. The cover is hinged on the top but may be hinged on the side. A plastic terminal block is mounted within the volume defined by the case. The terminal block includes terminal lugs to which wires may be connected. The terminal lugs in turn are electrically connected to female jaws or stabs within the terminal block. The female stabs are located within a receptacle formed in the terminal block. A pullout handle assembly is dimensioned to fit within the receptacle and includes knife blades which are electrically interconnected within the handle assembly. When the pullout handle assembly is inserted into the receptacle, the knife blades of the handle assembly engage the female stabs and thereby complete the circuit. An internal plastic shield covers the terminal lugs once installation of the wires has been completed.
Other AC disconnect devices are shown in Smith U.S. Pat. No. 2,581,308, Coley et al. U.S. Pat. No. 3,955,709, DiMarco et al. U.S. Pat. No. 4,233,482, Hibbert et al. U.S. Pat. No. 4,675,782, Hibbert et al. U.S. Pat. No. 4,794,211, Reichow et al. U.S. Pat. No. 5,272,297, and Kuki et al. U.S. Pat. No. 5,842,560.
The prior art AC disconnect switches have several shortcomings. The most consistent shortcoming of the prior art references is the relative inaccessibility of the terminal block within the case. In practice, AC disconnect switches are often mounted in locations where direct access may be limited. Therefore, it is important that the electrician wiring the AC disconnect switch have easy access from all angles to the terminal block and the terminal lugs of the terminal block. A case with a cover that only opens 90 degrees may often limit easy access to the terminal lugs of the terminal block. In addition, to facilitate wiring, the wiring from the air-conditioner compressor is often provided in the form of a wire harness which has it ends precut to a uniform length and stripped. In order to easily accommodate the preformed wiring harnesses, the terminal lugs should be aligned across the transverse direction of the AC disconnect switch case so that further cutting and stripping of the wires prior to installation is not required.
In addition, side opening AC disconnect switches may be mounted so that the location will not accommodate the opening of the cover in one direction. Therefore, an installer may have to maintain an inventory of AC disconnect switches that have both of left-hand opening covers and right-hand opening covers to accommodate particular installation locations.
The prior art also discloses AC disconnect switches with a locking mechanism to maintain the cover in a closed position on the case. One particular mechanism disclosed by the prior art is a protruding hasp attached to the case and engaging a slot in the cover. In the prior art, the protruding hasp is an impediment to packaging the AC disconnect switch in a rectangular box and thereby increases shipping volume.
In addition to the installation and drawbacks outlined above, the prior art AC disconnect switches are often unnecessarily complicated in their construction, requiring multiple screws for attaching the terminal block to the case and for attaching the cover to the case.
The present invention solves the above problems by providing an AC disconnect switch with an enclosure that provides improved access to the terminal block for the installer, improved adaptability to inaccessible installation locations, an improved locking mechanism, and simplified construction. In one embodiment of the present invention with a top opening cover, the case of the AC disconnect switch has portions of its side walls removed thereby exposing the sides of the terminal block for easier access. The AC disconnect switch has a cover that is hinged at the top of the case and opens at an angle greater than 180 degrees to further enhance installation access. In that same embodiment, the cover is provided with a detent mechanism that holds the cover open during wiring installation to further insured easy access for the installer. The AC disconnect switch further has the terminal lugs on the terminal block aligned in the transverse direction of the enclosure case to accommodate precut and prestripped wiring harnesses. The terminal lugs have roughened contact surfaces to insure good electrical contact between the terminal lugs and the wire. The terminal block is mounted to the case by a unique tab arrangement which requires only a single screw, the required ground screw, for installation of the terminal block within the case. The pullout handle assembly has a folding handle which minimizes the depth required for the case of the AC disconnect switch. Moreover, a locking mechanism has a retractable hasp at the bottom of the case that minimizes the shipping volume for the AC disconnect switch.
In a second embodiment of the present invention, the cover is hinged on the side of the case. The hinge arrangement requires no screws and instead snaps on and off the case. Consequently, the hinge arrangement allows for the cover to be hinged for either left-hand opening or for right-hand opening. Like the first embodiment, the second embodiment further has a single screw mounted terminal block with inline terminal lugs, roughened terminal lug contact surfaces, a folding handle to minimize depth, and a folding hasp to minimize shipping volume.
Therefore, it is an object of the present invention to provide an AC disconnect switch with an enclosure that provides improved access to the terminal block for the installer, improved adaptability to inaccessible installation locations, an improved locking mechanism, and simplified construction.
Further objects, features, and advantages will become apparent upon consideration of the following detailed description of the invention when taken in conjunction with the drawing and the appended claims.